Basic College Mathematics (10th Edition)

estimate - 32 exact - 31$\frac{43}{80}$
12$\frac{3}{5}$ + 8$\frac{5}{8}$ + 10$\frac{5}{16}$ Estimate : 12$\frac{3}{5}$ round to 13 8$\frac{5}{8}$ round to 9 10$\frac{5}{16}$ round to 10 So add 13+ 9 + 10= 32 is the estimate answer Exact : 12$\frac{3}{5}$ + 8$\frac{5}{8}$ + 10$\frac{5}{16}$ The least common multiple of 5, 8 and 16 is 80. Rewrite all the fractions as fractions with a least common denominator of 80. Rewrite as like fraction 12$\frac{3}{5}$ + 8$\frac{5}{8}$ + 10$\frac{5}{16}$= 12$\frac{48}{80}$ + 8$\frac{50}{80}$ + 10$\frac{25}{80}$ Add : 12$\frac{48}{80}$ + 8$\frac{50}{80}$ + 10$\frac{25}{80}$ Sum of the whole number is 30 and sum of the fraction is $\frac{123}{80}$ = 30$\frac{123}{80}$ The improper fraction $\frac{123}{80}$ is in lowest terms convert it into mixed fraction 1$\frac{43}{80}$, so the simplified sum is 30$\frac{123}{80}$ = 30 + 1$\frac{43}{80}$ = 31$\frac{43}{80}$ The estimate was 32, so the exact answer of 31$\frac{43}{80}$ is reasonable